ref: 3b8c62b683fc59abdc52d712bbe5a67017c28110
dir: /sys/games/lib/sudoku/boards/medium-2005-03-15.su/
......... ..7.1..45 659.27.3. 72...5... 3.......2 ...6...53 .8.24.517 27..6.8.. ......... 412358679 837916245 659427138 724835961 365194782 198672453 986243517 273561894 541789326